Impact of EUV multilayer mask defects on imaging performance and its correction methods

It is of tremendous impact with multilayer defects, which are caused by particles, substrate pits or scratches, in EUV lithography for the high volume manufacturing. Multilayer defects suppress the productivity and utilization rate of the mask blank. In this paper, we did a thorough investigation by conducting imaging simulations on dense and semi-dense patterns including lines and contact holes. The impact of isolated multilayer defects on the imaging of 22nm half-pitch dense line/contact and 33nm half-pitch semi-dense line has been studied, and the CD errors are calculated. The CD error, caused by the planar defect which is smoothed out during the multilayer deposition process, is found to be within ±10% of target values. This CD error can be compensated by adjusting the exposure dose or local pattern size. In contrast, the non-planar defect, which is not being smoothed in the multilayer surfaces, would lead to severe damages to the lithography performance.